Field
Embodiments of the present disclosure generally relate to an apparatus and method for processing semiconductor substrates. More particularly, embodiments of the present disclosure relate to an electrostatic chuck used in a plasma chamber.
Description of the Related Art
Plasma enhance processes, such as plasma enhanced chemical vapor deposition (PECVD) process, high density plasma chemical vapor deposition (HDPCVD) process, plasma immersion ion implantation process (P3I), and plasma etch process, have become essential in semiconductor processing. Plasma provides many advantages in manufacturing semiconductor devices. For example, using plasma enables a wide range of applications due to lowered processing temperature, plasma enhanced deposition has excellent gap-fill for high aspect ratio gaps and high deposition rates.
One problem that occurs during plasma processing is deformation of a substrate being processed, especially for a device substrate, i.e. a patterned substrate at high temperatures. Semiconductor devices are formed by stacking layers of materials by certain pattern on a semiconductor substrate. A patterned substrate may “bow” during processes due to differences in thermal expansion among layers of different materials, particularly when the substrate is being heated. Bowing of the substrate may lead to non-uniformity of the process surface. Sides and back of a bowed substrate may be processed which not only wastes processing material, as precursors for plasma processing are usually very expensive, but also causes contaminations and other troubles for subsequent process steps.
External means, such as an electrostatic chuck (ESC), are used to hold the substrate against the ESC surface during semiconductor processing so that the wafer would not move, and would keep consistent thermal and electrical contact with respect to the ESC. Most importantly, the ESC keeps the substrate flat during semiconductor processing. It is critical for PECVD applications that the substrate temperature and voltage be consistent during process and from substrate to substrate. It is of particular interest when the incoming substrate exhibits certain degree of compressive bow or tensile bow prior to being clamped to the ESC, and high operating temperature would further make the bow change, i.e., may be worse than the incoming bow due to substrate surface stress changes at high temperatures. In such a case, a chucked substrate may still become deformed during a plasma process due to high operating temperature.
Therefore, there is a need for an apparatus and method for clamping a substrate while maintaining flatness of the substrate during high operating temperature.